This invention relates to the art of electromagnetically operated fluid pumps, and more particularly to a new and improved electromagnetic pump which operates at extremely low power.
One area of use of the present invention is implantable drug delivery systems, although the principles of the present invention can be variously applied. The principal requirements for a pump in such applications are low power drain, since the pump must be driven by an implanted battery, and compatibility with the drug being pumped. Another important requirement is that the pump be capable of operating with bubbles present in the liquid being pumped. A related consideration is that the bubble pumping capability provided in the pump not give rise to inaccuracy caused by inertia of the fluid stream. Such inertial effect is a result of the momentum of the fluid stream being capable of maintaining motion of the stream for some time after completion of the pump piston stroke, and the fluid volume delivered as a result of the stroke is thereby increased. A further pump design consideration is providing a relatively small displacement pump which pumps bubbles in a manner equivalent to that of a larger displacement pump.
It would, therefore, be highly desirable to provide an electromagnetically operated pump which is safe, reliable, small in size, light in weight, which operates without excessive demand on the available energy supply, which is compatible with drugs or similar liquids to be pumped, which is capable of operating with bubbles present in the liquid being pumped, wherein the inertial effect on pump accuracy is reduced, and wherein the bubble pumping capability is not reduced by a reduction in pump displacement.